Rotary bit for wet drilling coal and the like



July 24, 1956 N. MacDONALD ROTARY BIT FOR WET DRILLING COAL AND THE LIKE Filed Feb. 17, 1954 ATTORNEY United States Patent ROTARY BIT FOR WET DRILLING COAL AND THE LIKE Norman MacDonald, Fraserburgh, Scotland, assiguor to Chicago Pneumatic Tool Company, New York, N. Y., a corporation of New Jersey Application February 17, 1954, Serial No. 410,998

2 Claims. (Cl. 255-61) This invention relates to rotary drill bits such as are employed in the wet drilling of coal, stone, and other hard substances, and it refers more especially to those bifurcated rotary drill bits which embody a pair of oppositely disposed cutting blades or wings integral with and extending from a tubular shank through which water or other liquid is led for delivery adjacent to the cutting edges of the bit for the purpose of assisting the drilling operation.

It is sometimes found in practice that with rotary drill bits of the kind referred to the swarf or cuttings of the material being drilled tends, under the drilling pressure, to obstruct partially or completely the liquid supply, with results that are detrimental to the drill bit and the drilling operation, and the principal object of the present invention is to overcome this disadvantage.

According to the invention a bifurcated rotary drill bit for use in the fwet drilling of coal, stone and other hard substances, embodying a pair of oppositely disposed cutting blades or wings integral with and extending from a tubular shank on opposite sides of a plane containing the axis of rotation of the drill, is formed internally of each blade or wing with a conduit adapted to deliver liquid through the circumferential surface behind (in reference to the direction of rotation) the cutting edge of the blade or wing. To this end a liquid conduit is disposed longitudinally within each cutting blade with the inner extremity of thevconduit in communication with the bore of the shank of the bit and with the outer extremity of the conduit debouching from the circumferential surface of each wing which is backed off from the leading edge of the wing to provide clearance in the borehole.

The point of emergence of each conduit from the surface of its respective cutting blade is preferably located at a suflicient distance from the operative extremity of the drill bit to ensure that the conduits are unalfected by any reduction in the length of the cutting blades which may be occasioned by wear of the tool when in use or by grinding the tool for sharpening purposes.

The invention is illustrated, by way of example, in the accompanying drawings, in which Figure 1 is a front view, Figure 2 is a section on line 2-2 of Figure 1, and Figure 3 is a side elevation of a drill bit.

A is a liquid supply passage that is drilled axially of the stem or shank B of the bifurcated drill bit and a short distance into the metal constituting the root of the wings or cutting blades D, and a passage E is drilled angularly through each cutting blade D towards and to connect with the axial passage A in the shank. A substantially Y-shaped liquid conduit is thus formed internally of the drill bit with the extremities of the two di- 5 vergent passages emerging on the radiused outer circumferential surface F which is backed off from the lead- Patented July 24, 1956 2 ing edge G of each wing, whereby the liquid is delivered adjacent to the actual cutting edges of the drill bit and the risk of the passages becoming choked or blocked is reduced to a minimum since each of the passages is disposed at an angle to the direction in which drilling pressure is exerted. Each wing D is fitted with a tungsten carbide inset or cutting portion H.

The invention is designed for use in connection With hollow drill angers or rods adapted to receive the tubular shanks of the drill bits, and it is applicable to those rotary drill bits of the concentric type in which the extreme radii of the blades or wings are equal as well as to those of the eccentric type in which the extreme radii of the blades or wings are unequal.

What is claimed is:

l. A bifurcated rotary drill bit for use in wet drilling of hard substances, embodying a pair of oppositely disposed cutting wings integral with and extending longitudinally from a tubular shank on opposite sides of a plane containing the axis of rotation of the drill and having a fluid passageway formed internally of the tubular shank which diverges to enter each wing, each wing having lengthwise thereof a radially reduced circumferential surface portion, and each divergent passageway opening out upon the circumferential surface in close relation to a cutting edge formed lengthwise of the wing.

2. A drill bit for wet drilling in hard substances, designed to provide a flow of fluid through a conduit thereof to the side and end cutting edges of the bit as well as to the wall and bottom of the borehole during a drilling operation, and in a manner so that the conduit will not become clogged by cuttings, comprising a shank portion, a relatively thicker body portion integral with an end of the latter, a pair of wing members extending longitudinally from the body portion in spaced relation to one another, each wing having a flat longitudinal face positioned in reverse directional relation to the flat face of the other, a cutting blade mounted to each flat face and having end cutting edges and a leading cutting edge disposed longitudinally of the wing; wherein each wing is characterized by: a quadrant arcuate surface section longitudinally thereof and backed off radially from the leading cutting edge so as to provide a clearance between the surface of the arcuate section and the opposed wall of the borehole in a drilling operation, and a Y fluid conduit having a stem passage extending through the shank and partway into the body portion of the bit and having branch passages extending angularly, one through each wing member so as to emerge through the arcuate surface at a point short of the leading cutting edge and about midway down the arcuate surface of the wing, whereby fluid (in reference to the direction of rotation) passed through a wing member simultaneously follows the leading cutting edge, scrubs the opposed wall of the borehole, and flows down the clearance between the latter and the arcuate surface to the end cutting edges and the bottom of the borehole.

References Cited in the file of this patent UNITED STATES PATENTS (1st addition to No, 955,696) 

